Electrodes of an IPS-LCD are aligned in such a manner that an electric field is applied in parallel to a liquid crystal plane of the IPS-LCD. Surfaces of a liquid crystal layer adjacent to two substrates have pretilt angles in a range of 0° to 5° as disclosed in U.S. Pat. No. 6,078,375. An IPS panel (liquid crystal cell) has an active matrix drive electrode comprising a pair of electrodes aligned in the same plane. In addition, the active matrix drive electrode provides IPS (In-Plain Switching), S-IPS (Super-In-Plain Switching) and FFS (Fringe Field Switching) modes to a liquid crystal layer formed between two glass substrates. According to the S-IPS mode, a two-domain liquid crystal alignment can be obtained by forming a zig-zag type electrode pattern, so an IPS color shift in a white state(Bright State) may be minimized.
The IPS-LCD is disclosed in U.S. Pat. No. 3,807,831. However, the IPS-LCD disclosed in U.S. Pat. No. 3,807,831 does not use a compensation film. Accordingly, the IPS-LCD represents a low contrast ratio at a predetermined inclination angle due to a relatively great amount of light leakage.
U.S. Pat. No. 5,189,538 discloses an LCD including two kinds of retardation films, such as a +A-plate and a positive biaxial retardation film, but it does not disclose information or technologies about the IPS-LCD.
U.S. Pat. No. 5,440,413 discloses a TN-LCD having two positive biaxial retardation films in order to improve the contrast characteristic and color characteristic of the TN-LCD at a predetermined inclination angle.
An IPS-LCD compensation film using one positive biaxial retardation film is disclosed in U.S. Pat. No. 6,285,430. Characteristics of the IPS-LCD are as follows:                One positive biaxial retardation film is aligned between a polarizer plate and a liquid crystal layer.        An in-plane retardation value of the biaxial retardation film is about 190 nm to 390 nm.        An in-plane retardation value of the biaxial retardation film increases in proportional to an absolute value of a retardation in a direction of thickness of a polarizer plate protection film.        
A main object of using the biaxial retardation film is to improve a contrast characteristic of the IPS-LCD at an inclination angle in all azimuthal angles, especially 45°, 135°, 225° and 315°. Although the contrast characteristic of the IPS-LCD can be improved at the above azimuthal angles, the IPS-LCD in a black state represents a great amount of light leakage at other azimuthal angles. For this reason, a contrast ratio of the IPS-LCD is relatively reduced at other azimuthal angles. Therefore, the above IPS-LCD has a disadvantage in that the IPS-LCD represents a relatively low contrast ratio at specific azimuthal angles due to relatively great light leakage in the black state.